Roll end detector

ABSTRACT

In order to determine when a roll of web material, such as paper, wound on a core has reached its end, a photoelectric detecting circuit is provided. The photoelectric apparatus is shown in combination with an electrostatic copying machine and includes a pair of photocells in a bridge circuit. One photocell receives light directly from a source while the other receives light reflected from the surface of a roll of web material. When the web material has been unwound to expose a core of a different color, the intensity of the reflected light changes causing the bridge circuit to become unbalanced, which unbalance is amplified and utilized to operate control means.

D United States Patent 91 11 3,709,604 Niesen et al. [451 Jan. 9, 1973 ROLL END DETECTOR 2,296,048 9/1942 Planskoy 95/89 AR [76] Inventors: George P. Niesen, 8131 Elmore 3,468,605 10/1969 Martin ..35S/28 Street, Niles, 111.; M00 S. Yoon, 1004 Rolling Ross, Glenview, n1. gf' 'g f l g y 6025 Attorney-McDougall, Hersh & Scott [22] Filed: July 20, 1970 [21] Appl. No.: 56,585 [57] ABSTRACT In order to determine when a roll of web material, such as paper, wound on a core has reached its end, a 250/219 photoelectric detecting circuit is provided. The I photoelectric apparatus is shown in combination with [581 of Search 250/220 an electrostatic copying machine and includes a pair 250/219 WE; 95/89 AR of photocells in a bridge circuit. One photocell receives light directly from a source while the other [56] References C'ted receives light reflected from the surface of a roll of UNITED STATES PATENTS web material. When the web material has been unwound to expose a core of a different color, the intenl,957,889 5/1934 Hopkins et a1. ..355/64 sity of the reflected light changes causing the bridge 2,613,692 10/1952 Anderson ..250/2l9 WE circuit to become unbalanced, which unbalance iS 8m- 2,215,21 1 9/1940 Devol ..2$0/222 X and utilized to operate control means. 2,292,825 8/1942 Dilks,Jr..., ..355/64 3,325,649 6/1967 Bird ..250/222 X 3 Claims, 3 Drawing Figures I 22 All 20 6 1- I I 52% l 7 5: i

BACKGROUND OF THE INVENTION This invention relates generally to apparatus for detecting changes in condition. More specifically, it relates apparatus for detecting the end of a roll of web material being unwound from a core.

In many types of machines web material, such as paper, is unwound from a roll and passed through apparatus which performs various operations on it. Very frequently the material is cut into sheets prior to or after the operations and it is desired that the sheets be of a certain size, which size may be varied.

A particular machine wherein such functions are performed is a copying machine for duplicating the image appearing on an original. In some machines of this type the paper onto which the image is to be copied is supplied from a roll of such paper and cut into sheets of desired lengths as copies are made. When the end of the roll is neared, a number of problems may arise. First, the paper remaining may not be long enough to make a complete copy of the original; and second, it may not be long enough to span the distance between the various means such as rolls, belts or the like for propelling the copy paper through the machine. In the event of the latter situation, the irregular length may remain in the machine and cause ajam when sheets cut from a new roll are fed through.

Another problem which may rise in the type of machine described comes when the machine is to make multiple copies of a single original. Machines having this capability usually have a counter which is preset to a desired number and the machine will make copies until that number is reached. Typically, the flash of an exposure lamp or movement of a feed motor or some such similar repetitively operating element will provide a signal serving as an input to the counter. Thus the counter may be recording that a copy has been made when such is not the case for the copy paper may have been exhausted from the roll.

In the prior art it has been proposed to provide a limit switch actuated by a feeler resting on the surface of the roll. As the diameter of the roll decreases, a point is reached where the switch will be actuated. While this solution is workable it suffers from the disadvantage of not being sensitive enough to insure that all ofa roll has been used so unnecessary waste results. In addition, being essentially a mechanical element, its positioning and adjustment are relatively critical and subject to change as the device is used.

Therefore, it is an object of this invention to provide a novel means for detecting the end of a roll of web material which utilizing essentially electrical components is accurate and reliable.

It is another object of this invention to provide a novel means for detecting the end of a roll of web material which insures that essentially all ofthe roll will be used, thus minimizing waste.

SUMMARY OF THE INVENTION The foregoing and other objects are achieved in an embodiment of the invention which utilizes elements sensitive to light reflected from the surface of a roll of web material or core on which it is wound together with means to provide an electrical signal effective to control operating elements when the core is exposed by unwinding the web therefrom and light is reflected from its surface.

BRIEF DESCRIPTION OF THE DRAWING The invention itself is set forth in the claims forming a part of this specification while an understanding of the structure and operation of an embodiment thereof may be obtained from the detailed description taken in conjunction with the drawing in which:

FIG. 1 is a partial sectional view showing the lightsensitive means in accordance with the invention;

FIG. 2 is a schematic illustration of apparatus in accordance with the invention embodied in a copying machine; and

FIG. 3 is a schematic diagram ofa circuit embodying part of the invention.

DETAILED DESCRIPTION FIG. 1 illustrates a portion ofa roll of web material 2 wound on a core 4. The material may be a roll of paper to be unreeled for use in a machine for making copies of original documents or may be some other kind of machine such as a printing press or the like. In order to utilize the invention the color of the web material should be different from the color of the core or have some other surface quality so that the light reflected from the surface of the web material will be different from the light reflected from the surface ofthe core.

The core may be mounted on any type of suitable spindle or shaft so as to permit the web material to be unwound therefrom. Mounted in the machine adjacent the roll on any suitable supporting surface 6 is a sensing head 8. The sensing head 8 is provided with a light socket 10 in which is mounted a light source 12 positioned within a chamber 14.

A first photocell 16 is mounted in an opening in the sensing head 8 which opening is provided with light access to the chamber 14 by means of a passage 18. Positioned on the other side of the sensing head 8 is a second photocell 20 aimed so as to respond to light reflected from the surface of the roll 2 or core 4. When apparatus in accordance with the invention is to be used with paper which is light sensitive, such as the zinc oxide coated paper used in copying machines, a filter 22 may be provided so as to permit passage of invisible portions of the light spectrum such as infrared and the photocells selected to be sensitive to such portions.

In operation light from the source 12 is caused to pass through the filter 22 and to be reflected from the surface of the roll 2 to the photocell 20. As the roll 2 is unwound from the core 4 its diameter of course constantly decreases so that the angle of reflection changes. However, the photocell 20 is positioned in such a way that substantially constant light is reflected upon it until the roll has been unwound exposing the surface of the core which, as pointed out, has different reflective properties so that a different amount of light is now reflected to the photocell 20. At the same time, a constant amount of light passes through the aperture 18 to impinge upon the surface of the photocell 16.

FIG. 3 illustrates a circuit for detecting when light is being reflected from the surface of the core and providing an electrical signal in response to such an event. This circuit includes the photocells connected as the arms of a bridge, the other two arms of which are constituted by the resistive element of a potentiometer 24. The bridge is supplied from a suitable source of electrical energy which in the illustrated embodiment is a direct current source. A slider 26 of the potentiometer 24 may be adjusted to balance the currents in the respective arms of the bridge circuit and to adjust its sensitivity. A first output 28 is provided between the potentiometer and photocell while a second output 30 is provided between the potentiometer and photocell 16. A suitable detecting circuit 32 receives the outputs 28 and 30 and is effective to provide a control signal in response to a change in conduction of the photocell 20 when the light reflected to that element changes because of the exposure of the core 4.

The detecting circuit may take any number of different forms. For instance, a differential amplifier responsive to currents flowing through the photocells l6 and 20 may be provided so as to produce one signal level when the currents are equal and a different signal level when the currents are unequal. Such an amplifier may be provided using solid state components such as transistors and the like. In addition, the output of such a differential amplifier may be connected to a threshold detector capable of providing an output signal when the input signal is in excess of a predetermined value. This will insure an operating signal of sufficient amplitude to effect a desired electrical operation. The particular detector circuit chosen may vary taking into consideration such factors as system gain, desired response time, availability of components, and the like.

The output of the detector 32 is supplied to a v switching device 34. The switching device 34 may be constituted by a transistor or SCR effective to conduct when the input signal to its control element is of sufficient amplitude and duration. Connected in series with the switching device 34 is the operating coil 36 of an electromagnetic relay the contacts of which may be arranged to control the state of energization of other circuits as desired.

If the photocells l6 and 20 are receiving equal amounts of light because the reflection to the photocell 20 is from the surface of the web material rather than from that of the core, then equal currents will be flowing therethrough. When the core is exposed because the material has been unwound completely therefrom and the surface of the core is such that less light is reflected to the photocell 20, the resistance of that photocell increases and less current flows therethrough. The difference in the current flow in the two arms of the bridge is therefore detected by the detector 32 which then supplies an electrical signal to the switching device 34 causing it to conduct. The conduction of the switching device 34 energizes the operating coil 36 causing the relay ofwhich it is a part to actuate its associated contacts.

A particular machine in which the invention has utility is a copying machine as shown in H6. 2. In this machine a roll of copying paper coated with a light-sensitive material such as zinc oxide is fed through a pair of rotating elements 38 provided with knife edges and over suitable guide rollers 40. The paper is then passed between a pair of charging electrodes 42 and 44 at which time an electrostatic charge is applied to the surface of the paper. After being charged the paper is transported by a belt conveyor 46 to a copying position. ln this position light from a source 48 is caused to be reflected from an original 50 through a suitable lens 52 onto the surface of the copying paper. The amount of light reflected from the original will of course vary in accordance with the images appearing on the surface of the original 50 and the zinc oxide coated surface of the copying paper will be selectively exposed in accordance with the images on the original.

After exposure the copying paper is transported by driven rollers 54 to a developing station 56 wherein the latent images created by the selective discharge of the copying paper will be developed. After developing, additional driven rollers 58 transport the copying paper to the outside of the machine.

Such a copying apparatus is of course controlled by suitable control circuitry including appropriate timers and switches. Such timers and switches are effective to control the actuation of the various operating elements such as the feed rollers, charging apparatus, and exposure lamp. In addition, the circuits also control a motor 60 driving the cutter blades 38 in order to sever the paper from the roll 2 into desired sheet lengths when copies are made.

As the end of the roll is approached it may be that there is insufficient paper left to provide a sheet length of desired size, in which case the copy will not be complete. In some circumstances the last remaining sheet length may not be long enough to span the distance between the various feeding elements so that it will remain in the machine and were a new roll to be provided and a new sheet severed from that roll, may butt against the remaining length of copying sheet causing the machine to jam. 7

ln accordance with this invention, the operating coil 36 is arranged to operate a movable contact 62 in the control circuit of the motor 60. As may be seen in FlG. 2 the contact 62 is normally closed. In addition, a normally opened contact 64 may be provided in the control circuit of a light 66. Thus, when the switching device 34 is operated in response to an output of the detector 32 indicating that the paper has unwound to the point where the core 4 is exposed, the coil 36 will be energized. Upon the energization of the coil 36 the contact 62 is opened. This prevents any further operation of the motor 60 and subsequently any further rotation or operation of the cutter blades 38 so that whatever paper is remaining on the roll 2 will be unwound and passed through the machine to exit from its other end. The detecting head 8 and cutter blades 38 are positioned relative to the other machine elements so as to insure that such remaining length is long enough to make a complete copy of the original and be conveyed out of the machine by the various transporting elements. In addition, this arrangement provides for a minimum of waste so that rolls of paper having several turns of material left thereon are not discarded.

At the same time the contact 62 is opened energizing the motor 60 the contact 64 is closed so as to complete the circuit to the light 66. The light 66 may be disposed on the outside of the machine so as to provide a visual indication to the operator that the end of the roll has been reached and a new roll should be provided. Obviously, the indicator may be audible or a combination of visible and audible means. Further, if desired, other contacts to be operated by the coil 36 may be provided to complete de-energizing the machine while the roll is being replaced. This particular feature may be useful as a safety measure and may be useful in those machines capable of making a multiple copy of a single original so that it does not continue to operate giving the operator the impression that copies are being made when such is not the case.

While the invention has been described in connection with a particular embodiment thereof, it is intended by the claims to cover all modifications and variations which fall within their scope.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a copying machine having means for supplying light sensitive copying paper from a roll of such paper; means for severing such paper unwound from the roll into desired lengths; means for exposing a severed length of such paper to an original to create a latent image of the original on the copying paper; and means for developing said latent image to cause it to become visible; the improvement comprising a light source; light-sensitive means exposed to said light source and to light substantially in the invisible portion of the light spectrum reflected from said source by the copying paper; means for supplying electrical energy to said light-sensitive means; circuit means responsive to current flow in said light-sensitive means to produce a control signal when current flow through said light-sensitive means changes in response to a variation in light reflected from the copying paper; and circuit control means responsive to the control signal to actuate a circuit control element when the control signal is produced.

2. The improvement of claim 1 wherein said lightsensitive means comprises a pair of photocells, means mounting one of said photocells so as to expose it to the light from said source; means mounting the other of said photocells so as to expose it to light reflected from the paper; and wherein means for supplying electrical energy includes a bridge circuit comprising a potentiometer and one of said photocells is connected in each of the arms of said bridge circuit.

3. The improvement of claim 2 including filter means passing only invisible portions of the light spectrum interposed between said other of said photocells and the roll of copying paper. 

1. In a copying machine having means for supplying light sensitive copying paper from a roll of such paper; means for severing such paper unwound from the roll into desired lengths; means for exposing a severed length of such paper to an original to create a latent image of the original on the copying paper; and means for developing said latent image to cause it to become visible; the improvement comprising a light source; lightsensitive means exposed to said light source and to light substantially in the invisible portion of the light spectrum reflected from said source by the copying paper; means for supplying electriCal energy to said light-sensitive means; circuit means responsive to current flow in said light-sensitive means to produce a control signal when current flow through said light-sensitive means changes in response to a variation in light reflected from the copying paper; and circuit control means responsive to the control signal to actuate a circuit control element when the control signal is produced.
 2. The improvement of claim 1 wherein said light-sensitive means comprises a pair of photocells, means mounting one of said photocells so as to expose it to the light from said source; means mounting the other of said photocells so as to expose it to light reflected from the paper; and wherein means for supplying electrical energy includes a bridge circuit comprising a potentiometer and one of said photocells is connected in each of the arms of said bridge circuit.
 3. The improvement of claim 2 including filter means passing only invisible portions of the light spectrum interposed between said other of said photocells and the roll of copying paper. 